The former Irish prime minister, toasted by leading Brexiters as a man who they could have done business with, has said he is “appalled” by what is happening in politics in Britain.

Enda Kenny, who gave way to Leo Varadkar last summer, said the British government’s position on Ireland “lacks credibility” and is “riven by dissent”. At a ceremony in Dublin, where he received an award for making an outstanding contribution to Europe, Kenny also lamented British business’s silence on the matter.

“The [British] government is riven by internal dissent, lacks credibility and clarity on the most serious issue in decades. Six months on from an agreement being reached in December last year, very little progress has been made,” he said. “The EU continues to negotiate from a unified position. British business is afraid to speak out because of the spectre of a Labour government,” he added.

His words will come as a sharp rebuke to Brexiters including members of the DUP who have said that if Kenny were still in power there would not be the problems with the Irish border.

In March, Jacob Rees-Mogg said “mature” and “responsible” Kenny’s “common sense approach” had been replaced by a “irresponsible vote-catching” Varadkar.

His remarks came as Varadkar suggested there could be an extension to article 50 if it looked as if there was no deal in sight.

“You’ll know that there are a number of different scenarios that could arise if we’re in a ‘no-deal’ situation. For example, it is possible to extend article 50 to allow more time for negotiations to take place. There is the possibility of an interim deal, or a transition period, pending an outcome or final negotiations over the transition period,” he told TV3.

The Irish prime minister said suggestions that the talks go to the wire with a deal sealed in the small hours of the morning were wide of the mark.

“I’ve heard some people talking about the possibility of a crunch late-night meeting in Brussels in late October, something akin to a last-minute budget compromise or a fisheries council,” Varadkar added.

“That of course, as [Kenny] pointed out, will not be the case – because when the EU member states, the 27 of us, discuss Brexit, we discuss it without the UK in the room. So this won’t be a drafting session – we’ll have to have agreement in advance of the summit in October.”

He said Kenny’s suggestion that there could be an extra summit, perhaps in September, October or even November, to help seal a deal was “helpful”.